diff --git a/usr.bin/write/write.c b/usr.bin/write/write.c index 2008fd2d80fa..0bf08b4b2b19 100644 --- a/usr.bin/write/write.c +++ b/usr.bin/write/write.c @@ -46,12 +46,16 @@ static char sccsid[] = "@(#)write.c 8.1 (Berkeley) 6/6/93"; __FBSDID("$FreeBSD$"); #include +#include +#include #include #include -#include #include + +#include #include #include +#include #include #include #include @@ -64,23 +68,76 @@ __FBSDID("$FreeBSD$"); #include void done(int); -void do_write(char *, char *, uid_t); +void do_write(int, char *, char *, const char *); static void usage(void); -int term_chk(char *, int *, time_t *, int); +int term_chk(int, char *, int *, time_t *, int); void wr_fputs(wchar_t *s); -void search_utmp(char *, char *, char *, uid_t); +void search_utmp(int, char *, char *, char *, uid_t); int utmp_chk(char *, char *); int main(int argc, char **argv) { + unsigned long cmds[] = { TIOCGETA, TIOCGWINSZ, FIODGNAME }; + cap_rights_t rights; + struct passwd *pwd; time_t atime; uid_t myuid; int msgsok, myttyfd; char tty[MAXPATHLEN], *mytty; + const char *login; + int devfd; (void)setlocale(LC_CTYPE, ""); + devfd = open(_PATH_DEV, O_RDONLY); + if (devfd < 0) + err(1, "open(/dev)"); + cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_LOOKUP, + CAP_PWRITE); + if (cap_rights_limit(devfd, &rights) < 0 && errno != ENOSYS) + err(1, "can't limit devfd rights"); + + /* + * Can't use capsicum helpers here because we need the additional + * FIODGNAME ioctl. + */ + cap_rights_init(&rights, CAP_FCNTL, CAP_FSTAT, CAP_IOCTL, CAP_READ, + CAP_WRITE); + if ((cap_rights_limit(STDIN_FILENO, &rights) < 0 && errno != ENOSYS) || + (cap_rights_limit(STDOUT_FILENO, &rights) < 0 && errno != ENOSYS) || + (cap_rights_limit(STDERR_FILENO, &rights) < 0 && errno != ENOSYS) || + (cap_ioctls_limit(STDIN_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || + (cap_ioctls_limit(STDOUT_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || + (cap_ioctls_limit(STDERR_FILENO, cmds, nitems(cmds)) < 0 && errno != ENOSYS) || + (cap_fcntls_limit(STDIN_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) || + (cap_fcntls_limit(STDOUT_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS) || + (cap_fcntls_limit(STDERR_FILENO, CAP_FCNTL_GETFL) < 0 && errno != ENOSYS)) + err(1, "can't limit stdio rights"); + + caph_cache_catpages(); + caph_cache_tzdata(); + + /* + * Cache UTX database fds. + */ + setutxent(); + + /* + * Determine our login name before we reopen() stdout + * and before entering capability sandbox. + */ + myuid = getuid(); + if ((login = getlogin()) == NULL) { + if ((pwd = getpwuid(myuid))) + login = pwd->pw_name; + else + login = "???"; + } + + if (cap_enter() < 0 && errno != ENOSYS) + err(1, "cap_enter"); + while (getopt(argc, argv, "") != -1) usage(); argc -= optind; @@ -99,29 +156,27 @@ main(int argc, char **argv) errx(1, "can't find your tty's name"); if (!strncmp(mytty, _PATH_DEV, strlen(_PATH_DEV))) mytty += strlen(_PATH_DEV); - if (term_chk(mytty, &msgsok, &atime, 1)) + if (term_chk(devfd, mytty, &msgsok, &atime, 1)) exit(1); if (!msgsok) errx(1, "you have write permission turned off"); - myuid = getuid(); - /* check args */ switch (argc) { case 1: - search_utmp(argv[0], tty, mytty, myuid); - do_write(tty, mytty, myuid); + search_utmp(devfd, argv[0], tty, mytty, myuid); + do_write(devfd, tty, mytty, login); break; case 2: if (!strncmp(argv[1], _PATH_DEV, strlen(_PATH_DEV))) argv[1] += strlen(_PATH_DEV); if (utmp_chk(argv[0], argv[1])) errx(1, "%s is not logged in on %s", argv[0], argv[1]); - if (term_chk(argv[1], &msgsok, &atime, 1)) + if (term_chk(devfd, argv[1], &msgsok, &atime, 1)) exit(1); if (myuid && !msgsok) errx(1, "%s has messages disabled on %s", argv[0], argv[1]); - do_write(argv[1], mytty, myuid); + do_write(devfd, argv[1], mytty, login); break; default: usage(); @@ -170,7 +225,7 @@ utmp_chk(char *user, char *tty) * writing from, unless that's the only terminal with messages enabled. */ void -search_utmp(char *user, char *tty, char *mytty, uid_t myuid) +search_utmp(int devfd, char *user, char *tty, char *mytty, uid_t myuid) { struct utmpx *u; time_t bestatime, atime; @@ -185,7 +240,7 @@ search_utmp(char *user, char *tty, char *mytty, uid_t myuid) if (u->ut_type == USER_PROCESS && strcmp(user, u->ut_user) == 0) { ++nloggedttys; - if (term_chk(u->ut_line, &msgsok, &atime, 0)) + if (term_chk(devfd, u->ut_line, &msgsok, &atime, 0)) continue; /* bad term? skip */ if (myuid && !msgsok) continue; /* skip ttys with msgs off */ @@ -219,15 +274,13 @@ search_utmp(char *user, char *tty, char *mytty, uid_t myuid) * and the access time */ int -term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror) +term_chk(int devfd, char *tty, int *msgsokP, time_t *atimeP, int showerror) { struct stat s; - char path[MAXPATHLEN]; - (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); - if (stat(path, &s) < 0) { + if (fstatat(devfd, tty, &s, 0) < 0) { if (showerror) - warn("%s", path); + warn("%s%s", _PATH_DEV, tty); return(1); } *msgsokP = (s.st_mode & (S_IWRITE >> 3)) != 0; /* group write bit */ @@ -239,26 +292,21 @@ term_chk(char *tty, int *msgsokP, time_t *atimeP, int showerror) * do_write - actually make the connection */ void -do_write(char *tty, char *mytty, uid_t myuid) +do_write(int devfd, char *tty, char *mytty, const char *login) { - const char *login; char *nows; - struct passwd *pwd; time_t now; - char path[MAXPATHLEN], host[MAXHOSTNAMELEN]; + char host[MAXHOSTNAMELEN]; wchar_t line[512]; + int fd; - /* Determine our login name before we reopen() stdout */ - if ((login = getlogin()) == NULL) { - if ((pwd = getpwuid(myuid))) - login = pwd->pw_name; - else - login = "???"; - } - - (void)snprintf(path, sizeof(path), "%s%s", _PATH_DEV, tty); - if ((freopen(path, "w", stdout)) == NULL) - err(1, "%s", path); + fd = openat(devfd, tty, O_WRONLY); + if (fd < 0) + err(1, "openat(%s%s)", _PATH_DEV, tty); + fclose(stdout); + stdout = fdopen(fd, "w"); + if (stdout == NULL) + err(1, "%s%s", _PATH_DEV, tty); (void)signal(SIGINT, done); (void)signal(SIGHUP, done);